1. Field of the Invention
The present invention relates to a wireless data service in a mobile communication system, and more particularly to a system and method for providing a wireless data service in a broadcast mobile communication system without any limitation of system resources regarding the number of terminals in use.
2. Background of the Related Art
The concept of providing cellular mobile communications in a coverage area divided into cells was developed by Bell Laboratories at the end of the 1960s. In 1983, the FCC, in controlling the development of the first generation analog mobile communications system, assigned 666 bi-directional channels of 800 MHz for the US AMPS (Advance Mobile Photo Services).
In 1991, US Digital Cellular (IS-54) was made available as a second-generation analog mobile communication system. This standard was based on a TDMA (time division multiple access) system using π/4 DQPSK (differential quadrature phase shift keying) digital modulation mode capable of assigning three users per 30 KHz channel by the AMPS, which is the Fm/FDMA(frequency division multiple access) mode. Application of the half-rate coding technique and the digital signal process at the same time has made it possible to process six users in a same bandwidth of 30 KHz.
The above-mentioned mobile communication technology continues to develop at a fast rate, and has resulted in the IMT-2000 which is the mobile communication system for the next generation. This system and others like it not only carry text and voice but also moving picture data. As the demand for wireless telephones increases, providing voice and data services to mobile terminal units will become a necessity.
A wireless data service should provide all services that are provided in existing PSTNs (public switched telephone network) and PSDNs (packet data service node), including information search, internet connection, enterprise computer connection, and facsimile transmission/receipt through a PC communication connection in addition to traditional file transmission. These basic services have spawned the development of a new class of specialized services, including transmitting field reports of new media, transmitting/receiving e-mails, and transmitting business reports of outdoor service employees such as insurance canvassers or A/S employees.
FIG. 1 is a block diagram illustrating a mobile communication system of a conventional wireless data service. The system includes a mobile communication terminal 10 such as a notebook, a PDA and/or a cellular phone which receives a wireless data service through the wireless communication system; a mobile communication system (A) including a base transceiver station (BTS) 20 for performing wireless communications with the mobile communication terminal 10, a base station controller (BSC) 30 connected to the base transceiver station 20 for controlling each base transceiver station, and a mobile switching center (MSC) 40 connected to a number of base station controllers 30 for controlling the whole system. Also included is an inter-working function/packet data service node (MN or PSDN) 50 which is connected to the mobile switching center 40 for providing the wireless data service. The inter-working function/packet data service node 50 may be connected to a data service center 60 or the Internet, to thereby provide the data required by a user. For illustrative purposes, the inter-working function/packet data service node is shown connected to the Internet to provide the data that the user requires.
FIG. 2 is a flow chart illustrating the operation sequence of a wireless data service method in the conventional mobile communication system. In a first step, if the mobile communication terminal 10 sends a call to request a wireless data service and terminal information to the base transceiver station 20 (S11), the base transceiver station 20 assigns a basic channel to the mobile communication terminal 10 (S12) and transmits a corresponding call to the base station controller 30 to request data from the inter-working function/packet data service node 50 in the base station controller 30 (S13).
The base station controller 30 also assigns channels according to the volume of wireless data requested by the mobile communication terminal 10 to provide the data (S14). The mobile communication terminal 10 receives the data through the connected channels (S15).
The above-mentioned mobile communication system has been developed as a mobile communication system to support the CDMA 2001x standard, which forms a basis for providing wireless remote multimedia casting service in the IMT-2000 network. In providing this service, a request for moving picture data is performed by establishing a connection to the wireless internet and selecting the wireless data service through a web browser in the terminal where the IMT-2000 service is receivable. In response to this request, a multicast group is logged in the inter-working function/packet data service node in the IMT-2000 network, a multicast tree is formed among each of the group sources, moving picture information transmitted from the inter-working function/packet data service node is compressed and encoded, and the information is transmitted to the terminal. The moving picture and voice information can then be provided through the wireless internet in a number of terminals, by using the multicast mode wherein the terminal receiving the data transmits the data to another terminal connected with the multicast tree and by reducing a use of the system resources.
The above-mentioned technique has the effect of reducing the load of the system resources, compared to the unicast mode of sending data to one specific person. However, as the number of subscribers of the mobile communication increase, the conventional wireless data service method may not be able to provide all subscribers with requested data services due to limited system resources. These limited system resources include the mode of assigning channels based on data service requests by mobile communication terminals and transmitting data.
Further, even though data is transmitted and received using the multicast mode, the point-to-point mode of transmitting data is restricted because it is unable to consistently provide a variety of data at a time to a lot of subscribers. In providing wireless data services, conventional systems also require additional equipment such as the inter-working function/packet data service node. This increases the cost and complexity of the system.